Changes in the future summer Mediterranean climate: contribution of teleconnections and local factors

Barcikowska, Monika; Kapnick, Sarah B.; Krishnamurty, Lakshmi; Russo, Simone; Cherchi, Annalisa; Folland, Chris K.

doi:10.5194/esd-11-161-2020

Cited by 40 publications

(44 citation statements)

References 78 publications

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“…Such compound events can lead to socio-economic damage exceeding that expected if the individual hazards were to occur separately (e.g. de Ruiter et al, 2020; Barriopedro et al, 2011). The MED region is highly vulnerable to compound heat-related events, such as the cooccurrence of heatwaves and droughts (Manning et al, 2019;Zampieri et al, 2017;Li et al, 2009).…”

Section: Introductionmentioning

confidence: 99%

Compound warm–dry and cold–wet events over the Mediterranean

et al. 2020

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Abstract. The Mediterranean (MED) Basin is a climate change hotspot that has seen drying and a pronounced increase in heatwaves over the last century. At the same time, it is experiencing increased heavy precipitation during wintertime cold spells. Understanding and quantifying the risks from compound events over the MED is paramount for present and future disaster risk reduction measures. Here, we apply a novel method to study compound events based on dynamical systems theory and analyse compound temperature and precipitation events over the MED from 1979 to 2018. The dynamical systems analysis quantifies the strength of the coupling between different atmospheric variables over the MED. Further, we consider compound warm–dry anomalies in summer and cold–wet anomalies in winter. Our results show that these warm–dry and cold–wet compound days are associated with large values of the temperature–precipitation coupling parameter of the dynamical systems analysis. This indicates that there is a strong interaction between temperature and precipitation during compound events. In winter, we find no significant trend in the coupling between temperature and precipitation. However in summer, we find a significant upward trend which is likely driven by a stronger coupling during warm and dry days. Thermodynamic processes associated with long-term MED warming can best explain the trend, which intensifies compound warm–dry events.

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Section: Introductionmentioning

confidence: 99%

Compound warm–dry and cold–wet events over the Mediterranean

et al. 2020

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“…Cold spells are a major weather-related hazard, causing premature excess mortality (Peterson et al 2013;Ballester et al 2016;Ryti et al 2016), agricultural losses (e.g., Ferrarezi et al 2019) and ecosystem damage (Boucek et al 2016). The Eastern Mediterranean has been identified as a climate change hot-spot (Giorgi 2006;Barcikowska et al 2020) and, although it is typically associated with warm weather and heat waves, has experienced damaging cold spells in recent decades. Moreover, the frequency of colds spells may not decrease as fast as may be naively expected under global warming, since variability may also increase (Kodra et al 2011;Gao et al 2015).…”

Section: Introductionmentioning

confidence: 99%

Dynamics and predictability of cold spells over the Eastern Mediterranean

et al. 2020

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The accurate prediction of extreme weather events is an important and challenging task, and has typically relied on numerical simulations of the atmosphere. Here, we combine insights from numerical forecasts with recent developments in dynamical systems theory, which describe atmospheric states in terms of their persistence (θ−1) and local dimension (d), and inform on how the atmosphere evolves to and from a given state of interest. These metrics are intuitively linked to the intrinsic predictability of the atmosphere: a highly persistent, low-dimensional state will be more predictable than a low-persistence, high-dimensional one. We argue that θ−1 and d, derived from reanalysis sea level pressure (SLP) and geopotential height (Z500) fields, can provide complementary predictive information for mid-latitude extreme weather events. Specifically, signatures of regional extreme weather events might be reflected in the dynamical systems metrics, even when the actual extreme is not well-simulated in numerical forecasting systems. We focus on cold spells in the Eastern Mediterranean, and particularly those associated with snow cover in Jerusalem. These rare events are systematically associated with Cyprus Lows, which are the dominant rain-bearing weather system in the region. In our analysis, we compare the ‘cold spell Cyprus Lows’ to other ‘regular’ Cyprus Low days. Significant differences are found between cold spells and ‘regular’ Cyprus Lows from a dynamical systems perspective. When considering SLP, the intrinsic predictability of cold spells is lowest hours before the onset of snow. We find that the cyclone’s location, depth and magnitude of air-sea fluxes play an important role in determining its intrinsic predictability. The dynamical systems metrics computed on Z500 display a different temporal evolution to their SLP counterparts, highlighting the different characteristics of the atmospheric flow at the different levels. We conclude that the dynamical systems approach, although sometimes challenging to interpret, can complement conventional numerical forecasts and forecast skill measures, such as model spread and absolute error. This methodology outlines an important avenue for future research, which can potentially be fruitfully applied to other regions and other types of weather extremes.

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confidence: 99%

“…A notable heat wave in recent years was the 2010 socalled "Russian heat wave", which caused ∼ 55 000 excess deaths in eastern Europe and western Russia (e.g., Barriopedro et al, 2011;Katsafados et al, 2014). The 2010 Northern Hemisphere summer saw a strong and persistent blocking ridge at 500 hPa over the Middle East and eastern Europe (e.g., Grumm, 2011;Schneidereit et al, 2012;Quandt et al, 2017), leading to unprecedented temperatures at numerous locations (Barriopedro et al, 2011). The eastern Mediterranean and Israel experienced a record-breaking (with respect to temperature) heat wave during mid-August of that year (https://ims.gov.il/sites/default/files/aug10.pdf, last access: 2 November 2020), which interestingly coincided with what is considered the decay phase of the Russian heat wave (Quandt et al, 2019).…”

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confidence: 99%

A new view of heat wave dynamics and predictability over the eastern Mediterranean

et al. 2021

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Abstract. Skillful forecasts of extreme weather events have a major socioeconomic relevance. Here, we compare two complementary approaches to diagnose the predictability of extreme weather: recent developments in dynamical systems theory and numerical ensemble weather forecasts. The former allows us to define atmospheric configurations in terms of their persistence and local dimension, which provides information on how the atmosphere evolves to and from a given state of interest. These metrics may be used as proxies for the intrinsic predictability of the atmosphere, which only depends on the atmosphere's properties. Ensemble weather forecasts provide information on the practical predictability of the atmosphere, which partly depends on the performance of the numerical model used. We focus on heat waves affecting the eastern Mediterranean. These are identified using the climatic stress index (CSI), which was explicitly developed for the summer weather conditions in this region and differentiates between heat waves (upper decile) and cool days (lower decile). Significant differences are found between the two groups from both the dynamical systems and the numerical weather prediction perspectives. Specifically, heat waves show relatively stable flow characteristics (high intrinsic predictability) but comparatively low practical predictability (large model spread and error). For 500 hPa geopotential height fields, the intrinsic predictability of heat waves is lowest at the event's onset and decay. We relate these results to the physical processes governing eastern Mediterranean summer heat waves: adiabatic descent of the air parcels over the region and the geographical origin of the air parcels over land prior to the onset of a heat wave. A detailed analysis of the mid-August 2010 record-breaking heat wave provides further insights into the range of different regional atmospheric configurations conducive to heat waves. We conclude that the dynamical systems approach can be a useful complement to conventional numerical forecasts for understanding the dynamics and predictability of eastern Mediterranean heat waves.

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Changes in the future summer Mediterranean climate: contribution of teleconnections and local factors

Cited by 40 publications

References 78 publications

Compound warm–dry and cold–wet events over the Mediterranean

Compound warm–dry and cold–wet events over the Mediterranean

Dynamics and predictability of cold spells over the Eastern Mediterranean

A new view of heat wave dynamics and predictability over the eastern Mediterranean

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